Antenna device

ABSTRACT

In an antenna device of the present invention, a plurality of antennas  21  are connected to a radio module  41  through respective coaxial cables  22 , and one or more of the antennas  21  in good communication conditions can be selected by the radio module  41 . An upper cabinet  2  is pivoted to a lower cabinet  4  through a three-dimensional joint  3 . The radio module  41  is contained in the lower cabinet  4 , while the plurality of antennas  21  are contained in the upper cabinet  2 . The plurality of coaxial cables  22  extending from the plurality of antennas  21  are tied in a bundle to pass through a through hole  34  provided in the three-dimensional joint  3 , and are connected to the radio module  41.

This application is the National Phase International ApplicationPCT/JP04/07804 filed May 28, 2004.

TECHNICAL FIELD

The present invention relates to an antenna device that receives radiowaves by a diversity method.

BACKGROUND ART

Diversity method antenna devices have been conventionally known thathave a plurality of antennas with different reception characteristicsand directivities, and select therefrom an antenna in the bestcommunication condition to receive radio waves (see JP 2002-237773, Aand JP 2002-271125, A, for example).

In the diversity method antenna devices, the plurality of antennas areconnected to a radio module through coaxial cables, and one or more ofthe antennas in good communication conditions are selected by the radiomodule. Therefore, good communication condition can be obtained even inthe case where reception radio waves vary in arrival direction withsurrounding environments or the case where reflected waves or diffractedwaves of the radio waves are received.

Alternatively, antenna devices have been known that can obtain goodcommunication condition by varying directions of an antenna (see JP9-246824, A and JP 6-47171, A).

For example, as shown in FIG. 5, an antenna device described in JP9-246824, A includes a telescopic antenna 9 slidably projecting from anend of a case 8. A recess 81 is defined at the end of the case 8, and anopening 82 is defined at a bottom of the recess 81. Inside the case 8, acylindrical antenna holder 83 is attached facing to the opening 82. Theantenna 9 has a first rod 911 having the largest diameter among aplurality of telescopic rod portions 91, the first rod 911 coupled to anantenna base 93 through a hinge mechanism 92. The antenna base 93 isslidably held by the antenna holder 83, and can rotate on the slidingdirection.

In the antenna device, the antenna 9 can be rotated by the hingemechanism 92 so as to be close to or apart from the case 8, while theantenna 9 can rotate on a central axis thereof to vary directions of arotation axis of the hinge mechanism 92. Therefore, the antenna 9 can bedirected in a direction of the highest reception sensitivity to therebyobtain good communication condition.

However, in the diversity method antenna devices, although an antenna inthe best communication condition can be selected from the plurality ofantennas, a direction of the antenna cannot be changed. Therefore, whena directivity of the antenna is out of an arrival direction of radiowaves, the best reception condition cannot be obtained.

In the antenna device capable of varying directions of the antenna asshown in FIG. 5, although the antenna can be directed in a direction ofthe highest reception sensitivity, inherent reception characteristics ofthe antenna cannot be changed. Therefore, when the receptioncharacteristics of the antenna are inappropriate for reception ofintended radio waves, the best reception condition cannot be obtained.

Accordingly, an object of the present invention is to provide an antennadevice capable of always realizing the best reception conditionregardless of arrival directions of radio waves or inherent receptioncharacteristics of each antenna.

DISCLOSURE OF THE INVENTION

In an antenna device of the present invention, a plurality of antennas21 are connected to a radio module 41 through respective cables, and oneor more of the antennas 21 in good communication conditions can beselected by the radio module 41. A movable case is pivoted to a basecase through a three-dimensional joint 3, and the radio module 41 iscontained in the base case, while the plurality of antennas 21 aredisposed in the movable case. The plurality of cables extending from theplurality of antennas 21 are tied in a bundle to pass through a throughhole 34 provided in the three-dimensional joint 3, and are connected tothe radio module 41.

In the above-described antenna device of the present invention, the basecase may be, for example, a part of a cabinet of a television receiver,or may be a separate cabinet fixed to the cabinet of the televisionreceiver. The three-dimensional joint 3 has freedom around each of threeaxes orthogonal to each other, and therefore can direct each of theplurality of antennas disposed in the movable case in any direction withthe base case fixed by inclining the movable case from front to back andfrom left to right, or rotating the movable case on a vertical axis.

When radio waves are transmitted or received, one or more of theantennas 21 in good communication conditions are first selected from theplurality of antennas 21 by the radio module 41. Next, in a receptioncondition of the selected antennas 21, a user varies directions of theantennas 21 while monitoring variations in reception sensitivity, andsets the antennas 21 to a direction of the highest receptionsensitivity. Thus, one or more of the antennas 21 in good communicationconditions are selected from the plurality of antennas 21, and the bestreception condition can be obtained by further directing the antennas 21in a direction of the highest reception sensitivity.

In a specific construction, the three-dimensional joint 3 includes apivot portion 31 projecting from one of the base and movable cases, aspherical portion 32 provided on an end of the pivot portion 31, and asphere receiving portion 43 provided in the other case, to which thespherical portion 32 fits so as to rotate freely. The through hole 34penetrates through the pivot portion 31 and the spherical portion 32 toopen to an inside of the one case and to an inside of the other case.

In the specific construction, the plurality of cables extending from theplurality of antennas in the movable case are tied in a bundle to enteran inside of the through hole 34 from an opening of the pivot portion 31of the three-dimensional joint 3, pass through the through hole 34, andreach from an opening of the spherical portion 32 to an inside of thebase case, and are connected to the radio module 41 in the base case.Therefore, the plurality of cables will vary in posture as the movablecase inclines while being tied in a bundle inside the through hole 34 ofthe pivot portion 31 and the spherical portion 32, and will not beentangled with each other.

As described above, according to the antenna device of the presentinvention, the best reception condition can always be realizedregardless of arrival directions of radio waves or inherent receptioncharacteristics of each antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an antenna device of the presentinvention;

FIG. 2 is a perspective view showing movements of an upper cabinet of anantenna unit in the antenna device;

FIG. 3 is a perspective view showing an internal structure of theantenna unit;

FIG. 4 is a sectional view of the antenna unit; and

FIG. 5 is a partially broken side view of a conventional antenna device.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention carried out to an antenna deviceof a television receiver will be specifically described below withreference to the drawings.

As shown in FIG. 1, the television receiver of the present inventionincludes a flat main body 1, and the main body 1 is supported by a base13. A flat display 11 is disposed on a surface of the main body 1, whilea pair of speakers 12, 12 are disposed below the display 11. An antennaunit 10 for receiving television broadcast waves is also attached to aback surface of the main body 1.

The television receiver is connected by a wireless LAN with a televisionbroadcast receiving device (not shown) installed indoors, and can outputvideo and audio of television broadcasts from the display 11 and thespeakers 12, 12 by receiving television broadcast waves transmitted fromthe television broadcast receiving device by the antenna unit 10.

As shown in FIGS. 2( a) and (b), the antenna unit 10 includes an uppercabinet 2 and a lower cabinet 4 each in the form of rectangularparallelepiped, and the both cabinets 2, 4 are coupled to each other bya three-dimensional joint 3. The upper cabinet 2 is thereby pivoted tothe lower cabinet 4. As shown, a user can incline the upper cabinet 2from front to back and from left to right relative to the lower cabinet4, and also can rotate the upper cabinet 2 on a vertical axis.

As shown in FIG. 1, the antenna unit 10 is attached to the main body 1of the television receiver with the lower cabinet 4 fixed to the backsurface of the main body 1 and the upper cabinet 2 projecting from anupper surface of the main body 1.

As shown in FIG. 3, inside the upper cabinet 2, five flat antennas 21with different reception characteristics and directivities are attachedto five surfaces except a bottom surface. Coaxial cables 22 withexcellent high-frequency characteristics are connected to the respectiveantennas 21.

As shown in FIG. 3 and FIG. 4, the three-dimensional joint 3 includes acylindrical pivot portion 31 penetrating the bottom surface of the uppercabinet 2 and attached to the upper cabinet 2, a spherical portion 32formed on a lower end of the pivot portion 31, and a sphere receivingportion 43 recessed from an upper surface of the lower cabinet 4, towhich the spherical portion 32 fits so as to rotate freely. Alarge-diameter portion 33 is formed on an upper end of the pivot portion31. A through hole 34 from an upper surface of the large-diameterportion 33 to a bottom of the spherical portion 32 is provided in thepivot portion 31 and the spherical portion 32. An opening of the throughhole 34 on the spherical portion 32 has an internal diameter graduallyexpanding downwardly.

The sphere receiving portion 43 of the lower cabinet 4 defines on abottom thereof an opening 44 having an internal diameter smaller than adiameter of the spherical portion 32 and larger than a diameter of theopening of the spherical portion 32. The through hole 34 of thethree-dimensional joint 3 is thereby opened to an inside of the lowercabinet 4 as well as an inside of the upper cabinet 2. The five coaxialcables 22 extending from the five antennas 21 in the upper cabinet 2 aretied in a bundle to penetrate through the through hole 34 of thethree-dimensional joint 3, and reach to the inside of the lower cabinet4 at ends thereof.

A radio module 41 is disposed inside the lower cabinet 4, and fiveterminal areas 42 are formed on an upper end of the radio module 41.Ends of the coaxial cables 22 are connected to the respective terminalareas 42. The five antennas 21 are thereby connected to the radio module41 through the five coaxial cables 22. Each of the coaxial cables 22extends from the respective antenna 21 to the radio module 41 with anappropriate allowance.

In the above-described antenna device of the present invention, thethree-dimensional joint 3 of the antenna unit 10 has freedom around eachof two orthogonal axes on a horizontal plane, and therefore can inclinethe upper cabinet 2 from front to back and from left to right relativeto the lower cabinet 4. The three-dimensional joint 3 also has freedomaround the pivot portion 31, and therefore can rotate the upper cabinet2 on the pivot portion 31. The upper cabinet 2 of the antenna unit 10can be thus directed in any direction relative to the main body 1 of thetelevision receiver, and each of the five antennas 21 contained in theupper cabinet 2 can be thereby directed in any direction.

In the above-described antenna device of the present invention, whentelevision broadcast waves are received from the television broadcastreceiving device, one or more of the antennas 21 in good communicationconditions are first selected from the five antennas 21 by the radiomodule 41. Next, in a reception condition of the selected antennas 21,the user varies directions of the upper cabinet 2 while, for example,checking picture quality of the display 11 to determine the directionwhere the best picture quality is obtained. The antennas 21 are therebyset to a direction of the highest reception sensitivity to realize thebest reception condition. Consequently, the display 11 displayshigh-quality video without noise, while the pair of speakers 12, 12 emithigh-quality audio without noise.

In the above-described antenna device of the present invention, the fivecoaxial cables 22 extending from the five antennas 21 in the uppercabinet 2 are tied in a bundle to enter the inside of the through hole34 from an opening of the pivot portion 31 of the three-dimensionaljoint 3, pass through the through hole 34, and reach from the opening ofthe spherical portion 32 to the inside of the lower cabinet 4, and areconnected to the radio module 41 in the lower cabinet 4. Therefore,these five coaxial cables 22 will vary in posture as the upper cabinet 2varies in posture while being tied in a bundle inside the through hole34, and will not be entangled with each other.

Each of the coaxial cables 22 extends between the antennas 21 and theradio module 41 with a sufficient allowance. Therefore, variations indirection of the upper cabinet 2 will not produce excessive tensionacting on the coaxial cables 22, and are unlikely to break the coaxialcables 22.

According to the above-described display device of the presentinvention, one or more of the antennas 21 in good communicationconditions are selected among the five antennas 21 by the radio module41. The upper cabinet 2 of the antenna unit 10 is rotated in acommunication condition of these antennas 21 to enable the antennas 21to be directed in a direction of the highest reception sensitivity.Therefore, the best reception condition can always be realizedregardless of arrival directions of radio waves or inherent receptioncharacteristics of each antenna.

The present invention is not limited to the foregoing embodiment inconstruction but can be modified variously within the technical scopeset forth in the claims. For example, the same effect as in theforegoing embodiment can be obtained by a construction in which thethree-dimensional joint 3 has the pivot portion 31 and the sphericalportion 32 projecting from the upper surface of the lower cabinet 4, andthe sphere receiving portion 43 recessed from the bottom surface of theupper cabinet 2. The same effect as in the foregoing embodiment can alsobe obtained by a construction in which the radio module 41 isincorporated in the main body 1 of the television receiver, while thesphere receiving portion 43 of the three-dimensional joint 3 is providedin the main body 1.

1. An antenna device comprising: a base case including a radio module, amovable case including a plurality of antennas, and a three-dimensionaljoint attached to said base case and said movable case, wherein aplurality of cables are attached to said plurality of antennas and saidradio terminal, and are bundled to pass through a through hole in saidthree-dimensional joint, and wherein said radio module selects one ormore of said plurality of antennas in order to maintain goodcommunication conditions wherein, the three-dimensional joint comprises:a pivot portion projecting from said movable case, a spherical portionprovided on an end of said pivot portion, and a sphere receiving portionprovided in said base case, to which said spherical portion fits so asto rotate freely, wherein said through hole penetrates through saidpivot portion and said spherical portion to open an inside of saidmovable case to an inside of the base case.
 2. An antenna devicecomprising: a base case including a radio module, a movable caseincluding a plurality of antennas, and a three-dimensional jointattached to said base case and said movable case, wherein a plurality ofcables are attached to said plurality of antennas and said radioterminal, and are bundled to pass through a through hole in saidthree-dimensional joint, and wherein said radio module selects one ormore of said plurality of antennas in order to maintain goodcommunication conditions wherein, the three-dimensional joint comprises:a pivot portion projecting from said base case, a spherical portionprovided on an end of said pivot portion, and a sphere receiving portionprovided in the movable case, to which said spherical portion fits so asto rotate freely, wherein said through hole penetrates through saidpivot portion and said spherical portion to open an inside of the basecase to an inside of the movable case.